b-AlanineÁ
/
oxalic acid (1:1) hemihydrate crystal: structure,
13
C
NMR and vibrational properties, protonation character
D. Godzisz, M. Ilczyszyn *, M.M. Ilczyszyn
Faculty of Chemistry, University of Wrocl aw, Joliot-Curie 14, 50-383 Wrocl aw, Poland
Received 26 March 2002; received in revised form 22 May 2002; accepted 22 May 2002
Abstract
The crystal structure of b-alanine Á
/
oxalic acid (1:1) hemihydrate complex has been reinvestigated by X-ray diffraction
method at 293 K. Formation of monoclinic crystal system belonging to C2/c space group and consisting of semi-
oxalate chains, diprotonated b-alanine dimers and water molecules bonded to both these units is confirmed. New results
are obtained for distances in the carboxylic groups and hydrogen bonds. These structural observations are used for
protonation degree monitoring on the carboxylic oxygen atoms. They are in accordance with our vibrational study. The
13
C NMR spectra provide insights into the solid structure of this complex, character of its hydrogen bonds and the b-
alanine protonation.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: b-Alanine Á
/
oxalic acid crystal; Vibrational spectra; Solid
13
C NMR; X-ray diffraction; DSC; Protonation; Hydrogen bond
1. Introduction
Family of simple amino acidÁ
/
acid crystalline
complexes (e.g. b-alanine, betaine, glycine and
sarcosine with organic or inorganic acids) seems
to be interesting for two reasons. Some of these
materials display a wealth of structural phase
transitions of various type and exhibit ferroelec-
tric, antiferroelectric or ferroelastic behaviour
[1,2]. In all of them hydrogen bond networks are
formed. Studies of the last phenomenon provide
information on properties of hydrogen bonds,
nature of protonation and principles of biomole-
cular aggregation. For these reasons we have
undertaken systematic studies on different com-
plexes of this category [3,4]. Our attention is paid
on crystal structure, vibrational and NMR proper-
ties of individual systems as well as on relations
between these spectroscopic and structural para-
meters in series of structurally similar crystalline
complexes.
This paper is devoted to the b-alanine Á
/
oxalic
acid (1:1) hemihydrate crystal properties. We
present its reinvestigated X-ray structure and
new FT-Raman, FT-IR and
13
C NMR data as
well as interpretation of the results. The titled
complex structure was published for the first time
during preparation of our manuscript but unfor-
* Corresponding author. Fax: '
/
48-71-328-2348
E-mail address: mi@wchuwr.chem.uni.wroc.pl (M.
Ilczyszyn).
Spectrochimica Acta Part A 59 (2003) 681 Á
/
693
www.elsevier.com/locate/saa
1386-1425/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
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